The present invention relates generally to laser scanners and, more particularly, to an optical window associated with a scanning face of a laser scanner and through which a laser beam is projected to define a scanning pattern for the laser scanner wherein at least one surface of the optical window is angularly supported relative to the scanning face to improve the incidence angles of the laser beam on the window and/or the refractive angles of the laser beam at the window.
Laser scanners for use at point-of-sale checkout counters in supermarkets and other retail stores are becoming more and more common as the reliability of scanners increases and their costs decrease. The scanners are commonly mounted within the checkout counters such that they have generally upwardly facing windows through which laser beams are projected in defined scanning patterns. A scanning pattern is created by a laser and associated optical components which produce a plurality of intersecting scan lines to define the pattern. A bar coded label including for example a UPC, EAN or JAN code on the packaging of a product presented at a counter is passed through the scan volume of a laser scanner, i.e. the volume extending beyond the face of the scanner within which bar coded labels can be successfully read. Light reflected from a bar coded label is received back through the scanning window and processed to identify the product and provide pricing information for the sale and other retailing applications such as inventory control.
The scanning volume of a laser scanner can be increased by increasing the size of scan mirrors which define the scan pattern for a given scanner, particularly the mirrors which define the vertical scan lines. Unfortunately, increasing the size of the scan mirrors tends to increase the scanner size and particularly the scanner depth which is undesirable. Even for scanner designs with large scan volumes, scuffs and scratches in the scanning window due to repeated dragging of packages, cans, bottles and the like thereover impede transmission through the window and thereby reduce the scan volume.
To overcome reduced scan volume due to scuffed and scratched scanning windows, existing bar code scanners may have two windows through which the scanning beam passes, an inner window which is fixed to seal and protect the scanner and an outer window which is easily replaceable. In this way, the original scan volume is periodically restored by replacing the outer window to eliminate the scuffs and scratches which interfere with scanner operation. Unfortunately, the outer windows need to be replaced frequently to maintain scanner operation within acceptable levels resulting in undesirable service expenses.
It is thus perceived that a need exists for a laser scanner having an enlarged scan volume for a defined size of scan mirrors such that the scanner size and particularly the scanner depth does not have to be increased to obtain the enlarged scan volume. Such an enlarged scan volume would also reduce the frequency of replacement of outer scanning windows. Preferably, such a laser scanner would facilitate use of a single scanning spaced inwardly from the face of the scanner such that the outer window can be eliminated which of course would also eliminate service expenses incurred for replacing the outer window.